Fuel supply systems of internal combustion engines for stationary or mobile machinery may utilize liquid or gaseous fuel. For example, diesel fuel may be used in a diesel engine to provide a desired torque and combustion efficiency. Gaseous fuel, such as natural gas, may be used in a gaseous fuel engine to provide adequate torque, while potentially achieving reduced cost due to a ready supply of natural gas at certain engine locations. Some internal combustion engines, known as dual-fuel engines, are configured to run on two different fuels. For example, some internal combustion engines can employ diesel fuel as a pilot fuel and natural gas as a primary fuel. When natural gas is used as a fuel, the natural gas may be stored in liquid form as liquid natural gas (LNG) in a pressurized storage tank. The level of LNG stored in the storage tank may be measured by a liquid level sensor, such as a capacitance level sensor. Further, the LNG is supplied to the engine as natural gas by maintaining a pressure in the storage tank and the fuel supply system above a minimum threshold. As the fuel in the storage tank is consumed by the engine, the level of LNG in the storage tank decreases. Eventually, the level of LNG will decrease below a threshold level such that the pressure in the fuel supply system will decrease below the minimum threshold for supplying natural gas to the engine. However, there may be residual LNG available in the storage tank even though there is not enough pressure to supply the natural gas remaining in the storage tank to the engine.
One problem with current storage tank systems is that the storage tank level and pressure inside the storage tank may not be well correlated during operation in mobile machinery applications. For example, the pressure in the storage tank depends on many factors, including saturated LNG temperature, liquid-vapor volume and mass ratio, LNG boil off rate due to heat transfer, sloshing of the fuel in the storage tank causing collapse of vapor pressure, and engine fuel consumption rate. Further, in systems that utilize a liquid level sensor, the operator may see the tank level indicator in the cab display a perceived usable tank level because of the residual LNG in the storage tank. However, the engine is not able to utilize the residual LNG in the storage tank due to the pressure being too low to supply natural gas to the engine. As such, the storage tank may be effectively empty while the tank level indicator indicates that there is LNG remaining in the storage tank. Various factors may also affect the accuracy of the tank level indicator. For example, capacitance of the liquid level sensor may change over time or the operator may use different types of gaseous fuels that have different dielectric constants.
U.S. Pat. No. 5,379,637, issued to Abowd on Jan. 10, 1995 (“the '637 patent”), describes a system and method of measuring and indicating a level of natural gas fuel in a storage tank of a motor vehicle. The system utilizes a pressure sensor for measuring pressure inside the tank and a temperature sensor for measuring temperature of the natural gas inside the tank. A control unit determines a command for a gauge indicative of the amount of fuel in the tank in response to the measured pressure and temperature. The '637 patent further discloses the control unit uses a look-up table to retrieve a signal representative of a percentage that the tank is full of the natural gas based on the measured pressure and temperature. As such, the system and method of the '637 patent indicates a level of natural gas fuel in the storage tank. However, the '637 patent does not disclose that the control unit indicates the tank as empty when there is residual LNG remaining in the tank that is not useable.
The systems and methods of the present disclosure may address or solve one or more of the problems set forth above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.